″The frequency and ferocity of these battles demonstrates the excessive, demented obstinacy of Tripoli,″ the statement said.

Chad says Libya supplies the rebel group, called the Legion, with arms and training. Libya denies the organization exists.

The rebels normally cross into western Chad from bases in the lightly populated Darfur province in eastern Sudan, where the Khartoum government exercises virtually no control.

Renewed fighting in the sporadic civil war broke out last month when rebels took government outposts at Bahai and Tine. Chadian troops later recaptured the positions.

The battles have caused France to reinforce its garrisons in eastern Chad with 146 paratroopers, a second transport aircraft and a military surgical unit. France had been stationing about 1,000 troops in its former African colony.

Libya, which once occupied most of northern Chad, was chased out three years ago in a series of defeats. Tripoli still claims as its own a strip of land on Chad’s northern border, the Aouzou Strip.

In a peace agreement signed last September, Libya and Chad reconfirmed their cease-fire, agreed to the exchange of prisoners of war and to submitting their territorial dispute to international arbitration.